This invention relates generally to a workpiece finishing system, and more particularly to a system for impinging and recycling a grit and fluid slurry used to finish a workpiece.
Traditionally, metal workpieces must be belted, polished and then buffed prior to plating. The conventional wisdom has been that any "item to be plated, if the plating is to be a bright plate, must be highly polished. The plating can be no brighter than the surface to which it is applied." C. W. Ammen, Electroplater's Handbook, 1986, page 69, published by Tab Books Inc. The belting employs a course grit belt, or wheel, which must be replaced approximately every five or six pieces. The polishing and buffing wheels also require extensive manual preparation, set up and replacement. The belting, polishing and buffing steps are typically performed by hand and must be very meticulously and uniformly done to ensure a bright base surface. However, the workplace is often extremely contaminated with oil and the like, and the operations are often tedious and time-consuming. Accordingly, part-to-part inconsistencies are prevalent, and labor and scrap costs are significant. Furthermore, an animal tallow, fatty acid and wax grease-stick compound is used on the polishing wheels to retain grit. A subsequent high temperature or acidic washing step is often employed in an attempt to remove the polishing compound, but with limited success. Any polishing compound remaining on the workpiece during plating leads to unacceptable plating adhesion to the base material, thus causing a very high scrap rate during plating.
It is also know to use a sand and water slurry to clean, but not finish, metal workpieces. An exemplary water and sand abrasive system is disclosed in U.S. Pat. No. 4,817,342 entitled "Water/Abrasive Propulsion Chamber" which issued to Martin et al. on Apr. 4, 1989. It is common for such systems to simply discard the water and inexpensive sand after each use. Moreover, the sand is not of a fine enough grit and sufficient hardness to adequately finish a workpiece for subsequent plating or for grit reuse.
Moreover, various slurry recycling systems have been attempted. For example, reference should be made to the following U.S. Patent Nos.: U.S. Pat. No. 5,791,970 entitled "Slurry Recycling System for Chemical-Mechanical Polishing Apparatus" which issued to Yueh on Aug. 11, 1998; U.S. Pat. No. 5,664,990 entitled "Slurry Recycling in CMP Apparatus" which issued to Adams et al. on Sep. 9, 1997; and U.S. Pat. No. 5,477,844 entitled "Slurry Recovery System for a Wet Cutting Saw" which issued to Meister on Dec. 26, 1995; all of which are incorporated by reference herewithin. However, none of these traditional systems exhibit the quick, efficient, cost effective and high performance characteristics of the present invention which is suitable for use on a variety of workpieces.